The use of unmanned air vehicles (UAV) has been increasing in both commercial and military applications in recent years. As UAV technology progresses, it has become apparent that air-to-air refueling capabilities may be necessary for UAVs. Current methods and systems for air-to-air refueling of other types of aircraft have not been easily applied to UAVs due to the nature of pilot control generally required in air-to-air refueling operations.
There are currently two primary systems for air-to-air refueling. One system is the boom refueling system. The boom refueling system typically comprises a rigid boom extended from a refueling aircraft. At one end of the boom is a refueling nozzle and adjacent the refueling nozzle are airfoils, which are controlled by a boom operator on the refueling aircraft. The airfoils provide maneuverability of the boom with respect to an aircraft that is to be refueled. For the aircraft that is to be refueled, the receiving aircraft, the pilot typically maneuvers the aircraft to within a sphere of radius aft and below the refueling aircraft, the tanker aircraft. Upon maneuvering into the sphere of radius, the boom operator controls the airfoils to position and mate the boom into a refueling connection on the receiving aircraft. As UAVs do not have pilots to precisely maintain position relative to the tankers, air-to-air refueling using boom refueling systems has to date not been accomplished.
Another type of refueling system is the probe and drogue system. In the probe and drogue system, a refueling hose having a drogue disposed on one end is trailed behind the tanker. The receiving aircraft has a probe that is flown by its pilot into the drogue. As the drogue typically moves away from the receiving aircraft as it approaches, great skill and maneuvering ability is required by the pilot to mate the probe with the drogue. Again, as UAVs do not have pilots, UAV, air-to-air refueling using probe and drogue systems has not previously been accomplished.
Optical systems have been devised in the past for positioning refueling drogues with respect to refueling probes. As refueling drogues, however, have proven relatively unmaneuverable, these systems have not been operationally viable. One such optical system is described in U.S. Pat. No. 5,326,052 to Krispin et al. Other optical systems for positioning objects with respect to reflectors and retro-reflectors have not been easily adapted to air-to-air refueling systems. Therefore, it would be desirable to have an air-to-air refueling system that utilizes optical positioning methods to position an unmanned air vehicle with respect to a refueling aircraft for both a boom refueling system and a probe and drogue refueling system. It would also be desirable to have a system that could be easily integrated into existing flight control systems on board UAVs so that the existing flight control systems can be responsive to an optical signaling system for positioning the UAV.